Re: Deprecating Hash Indexes

Simon,

> * Put WARNINGs in the docs against the use of hash indexes, backpatch
> to 8.3. CREATE INDEX gives no warning currently, though Index Types
> does mention a caution.

I'd be in favor of a warning on create index.

Also, are hash indexes replicated?

> * Mention in the current docs that hash indexes are likely to be
> deprecated completely in future releases. Should anybody ever make
> them work, we can change that advice quickly but I don't think we're
> going to.

I'm not sure that's true, necessarily. The nice thing about work on
hash indexes is that it's potentially rather self-contained, i.e. a good
GSOC project. However ...

> Personally, I would like to see them removed into a contrib module to
> allow people to re-add them if they understand the risks. ISTM better
> to confiscate all foot-guns before they go off and then re-issue them
> to marksmen, at the risk of annoying the people that use them with
> full knowledge but that's likely a contentious issue.

I would be in favor of moving them to contrib for 9.4. Assuming that
someone can figure out how this interacts with the existing system table
opclasses. Them being in /contrib would also put less pressure on the
next new hacker who decides to take them on as a feature; they can
improve them incrementally without needing to fix 100% of issues in the
first go.

So, +1 with modifications ...

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com